From Minecraft Parkour Wiki
- isn't assigned a value because it has no importance. By convention, the 0th tick corresponds to the player's initial velocity before jumping.
- corresponds to the initial jump motion. It is increased by 0.1 per level of Jump Boost
- Jump height is slightly higher in 1.9 due to the momentum threshold being reduced (old=1.249, new=1.252)
- Terminal velocity is -3.92 m/t
- When the player collides vertically with a block, vertical momentum is cancelled and only the acceleration is left.